1. Field
The following description relates to an inductor.
2. Description of Related Art
The wireless communication field has experienced rapid development of a variety of devices, such as mobile phones, wireless pagers, and devices utilizing satellite communication. As a result, due to the increased in demand caused by the rapid development, integrated circuits (ICs) such as monolithic microwave integrated circuits (MMICs) have become important. In an MMIC, a radio frequency (RF) circuit includes a passive element and an active element on a single semiconductor substrate. Accordingly, MMICs are able to be mass produced for various small and light wireless communication devices at a minimal cost.
Silicon is generally used in the fabrication of ICs. Due to a poor insulating characteristics and losses occurring through conductivity of a silicon substrate, passive elements may experiences losses. In the case of an inductor that is a passive element, a high substrate loss may occur due to low resistance of a silicon substrate, thereby possibly leading to signal attenuation.
In an example, an inductor characteristic is indicated as a quality factor Q. Q denotes a ratio of energy accumulated in a reactive element such as a capacitor or an inductor with respect to a sum of energy loss. An idealistic tuning circuit may include an inductor and a capacitor, and may accumulate energy by exchanging current from a single element to a subsequent element. Accordingly, an inductor having a good Q value may promote operational characteristics in an IC.
Even though an inductor is used to configure a frequency chip, in an example, the inductor occupies the largest area of the frequency chip as a single element and is affected by a high frequency characteristic resulting from a parasitic capacitance and a resistance component from a neighboring material, a structure, and an internal material. In this case, it may be beneficial to configure an inductor having a high Q, or a high inductance.
Accordingly, to enhance a Q of an inductor, various methods known to one of ordinary skill in the art have been employed, such as a method of decreasing a serial resistance of a metal line using a metal having a low specific resistance, a multilayered metal, a thick metal, and other suitable metals known to one of ordinary skill in the art, or a method of decreasing a substrate loss using pattern ground shielding.
The above methods may have some constraints. For example, different from a general metal wiring, an inductor is formed in an upper portion of an upper metal wiring and does not leave room for another element to be integrated in a lower portion of the upper metal wiring.
Further, in general, to form an inductor within an IC package, a package substrate may include bonding pads that are separate from input/output package pins. To receive the bonding pads, a size of an IC substrate needs to increase, thereby sacrificing integration.